> I’d be interested to compare their rates to Wise.
Well for US-based "no foreign transaction fees" credit cards the rate is 0. There's no additional fee. For cards with foreign transaction fees you'll see something like 1% that goes to Visa/Mastercard/whoever and then the bank will charge a fee too, typically a percent or two.
But that's one thing, and then you have the actual currency conversion rates. I found an excerpt from an article that I think explains it well enough [1].
"Typically, a purchase at a foreign merchant is made entirely in the local currency. The cardholder authorizes the purchase amount in the local currency, and the purchase price is not converted until the payment is processed.
When you make a purchase at an international store, you may be asked if you want to convert your purchase to your home currency. This service is provided at the point of sale as a value added service and allows you to know the converted price at that moment—but don’t be fooled; it comes at a cost.
While this may initially sound like a wise way to avoid fees, these charges are in addition to any foreign transaction fees your card may apply. These fees assessed by the merchant at the point of sale are called dynamic currency conversion or DCC. You can think of DCC as an added service and just like most services that make life easier, there’s a convenience charge. Plus, even when using DCC, you’ll usually be charged a foreign transaction fee by your card issuing bank unless your card has no foreign transaction fees."
tl;dr version is, at least for an American, get a "no foreign transaction fees" credit card and save 1%-3% on all transactions you may otherwise be charged a fee for, and if prompted by a local shop to exchange currency, don't, just pay in the local currency so they can't dishonestly set arbitrarily high exchange rates. Visa and Mastercard (among others) as mentioned in the article have better negotiated exchange rates so it's better to let them do any exchange that's needed to keep costs to a minimum.
[1] https://www.forbes.com/advisor/credit-cards/foreign-transact...